1. Field of the Invention
The present invention relates generally to the field of optical fiber communication and more particularly to the reconstruction of an optical fiber cable.
2. Background Art
In the past decade, applications involving optical fiber based communication systems are becoming more practical and are gradually replacing copper based systems. A common task required by these applications is to repair damaged fiber optic cables. There are three prior art technologies that are used to repair fiber-optic cables and the most relevant patents to this invention appear to be the one by Thomas Scanzillo, Aug. 10, 2004, U.S. Pat. No. 6,773,167; by Toshiyuki Tanaka, Oct. 5, 1999, U.S. Pat. No. 5,963,699 and by Bruno Daguet, and by Gery Marlier, May 24, 1994, U.S. Pat. No. 5,315,682. These patents are thereby included herein by way of reference.
A typical prior art fusion spliced optical fiber is illustrated in FIG. 1. The splice consists of an input optical fiber 110 with a protective coating 120, and an output optical fiber 115 with a protective coating 125. The optical fibers are joined at the interface 130 using an automated apparatus following precision alignment and discharge induced fusion splicing process. In order to protect the splicing region, a rigid rod 150 is used and typically the splice and the rigid rod are both enclosed in a heat shrinking enclosure 140.
An alternative prior art mechanical fiber-optic splice is illustrated in FIG. 2. The splice consists of an input optical fiber 210 with a protective coating 220, and an output optical fiber 215 with a protective coating 225, a capillary glass tube 250 containing a precision through channel, placed in side of a protective outer tube 240 and with protective end caps 260 and 265. Typically, the input and output fibers are placed inside of the glass capillary, an index matching fluid 230 is used to form an air free contact. For certain splices, there is an added small perpendicular channel in the capillary tube 255. To aid the fiber insertion into the glass capillary tube, two ends of the capillary tube are normally tapered to form interfacing cones. The inner diameter of the capillary tube is made substantially close to the outer diameter of the optical fiber with typical tolerances within one micrometer for a single-mode fiber splice, and a few micrometers for a multimode fiber splice. The index matching fluid is transparent and has a refractive index very close to that of the core of the optical fiber. Frequently, the optical fiber cable-splice interfaces are further protected by flexible boots 270 and 275. The prior art fiber splice is often protected with a plastic outer package (not shown) for mechanical stability.
A related prior art fiber optic cable is illustrated in FIG. 3. The cable consists of a coating protected optical fiber 310, a buffer tube 320, a layer of cable strengthening fibers 380 and an outer jacket 390. These cables are designed for reliable operation in challenging environments.
Although most of the commercially available fiber optic splices do not reconstruct the broken fiber optic cable, prior arts do exist for undersea cable reconstruction. In such a case, reconstruction is typically welded, very bulky and extensive to protect extreme undersea water pressure. Due to the small temperature fluctuations in the undersea environment, materials with substantially different coefficient of thermal expansion (i.e., stainless steel and copper) can be employed without compromising splice reliability.
These prior art approaches have several areas for improvements. For example, the plastic protective outer package of an optical fiber splice has a very limited range of operating temperature. Furthermore, in avionics applications, a fast temperature-cycled environment requires additional packaging considerations to ensure stable and reliable operations. Additionally, in order to splice fiber optic cables such as the one illustrated in FIG. 3, one must have structure improvements such that the mechanical and chemical resistance properties of the cable restored. Such a restoration needs to provide a compact packaging, mechanical and chemical integrity, as well as a thermal protection of fast changing environmental temperature. There is a need, therefore, to make improvements to these prior arts, so that highly reliable fiber-optic cable splices and reconstructed fiber-optic cables can be realized.